Magenta metal chelate dyes and their use ink-jet printers

ABSTRACT

A metal chelate compound of Formula (1) or a salt thereof: 
 
[A-N=N—B] M   Formula (1) 
wherein: A is an optionally substituted pyridyl ring; and 
 
B is of the Formula (2):  
                 
wherein: X and W are substituents other than H; M is a metal chelated to A-N=N—B; and n is 0 to 4, also claimed are compositions and inks containing a compound of Formula (1), a process for ink jet printing using the inks and an ink jet printer cartridge containing the ink.

This invention relates to metal chelate compounds, to inks and to theiruse in ink jet printing (“IJP”).

IJP is a non-impact printing technique in which droplets of ink areejected through a fine nozzle onto a substrate without bringing thenozzle into contact with the substrate.

There are many demanding performance requirements for dyes and inks usedin IJP. For example they desirably provide sharp, non-feathered imageshaving good water-fastness, light-fastness and optical density. The inksare often required to dry quickly when applied to a substrate to preventsmudging, but they should not form a crust over the tip of an ink jetnozzle because this will stop the printer from working. The inks shouldalso be stable to storage over time without decomposing or forming aprecipitate which could block the fine nozzle.

Colour ink-jet printers typically use four inks of differing hues:magenta, yellow, cyan, and black. Colours other than these may beobtained using differing combinations of these inks. Thus, for optimumprint quality, the colorants used must be able to form an ink with aspecific precise hue. This can be achieved by mixing colorants but isadvantageously achieved by used a single colourant with the exact huerequired.

Magenta colorants such as C.I. Acid Red 52 and their use in IJP areknown. Many magenta colorants have poor ozone and/or light fastness.Others have an undesirable shade or low chroma. Our own recent studieshave shown the deleterious effect ozone can have on prints, causingaccelerated fading even in the dark. With ever increasing manufacturerand customer requirements for long term print fastness there is a needfor magenta colorants suitable for ink jet with improved shade, lightfastness and ozone fastness

WO 01/48090 relates to metal chelate compounds that comprise a naphtholcomponent and certain heterocyclic groups. WO 01/48090 does not disclosesuch compounds substituted by a pyridyl ring attached to an azo group inthe alpha position. Furthermore, WO 01/48090 does not disclose the factthat such substituted compounds have superior properties for use in inkjet printing applications.

According to the present invention there is provided a metal chelatecompound of Formula (1) or a salt thereof:[A-N=N—B] M   Formula (1)wherein:

-   A is an optionally substituted pyridyl ring; and-   B is of the Formula (2):    wherein:-   X and W are substituents other than H;-   M is a metal chelated to A-N=N—B; and-   n is0to4.

A is preferably of the Formula (3):

wherein:

-   q is 0, 1, 2, 3 or4; and-   each Z independently is a substituent other than H.

Preferably W, X and Z are each independently selected from CF₃, —OH,—Br, —Cl, —F, —CN, —NO₂, phosphoric acid, sulpho, optionally substitutedphosphoramide, optionally substituted alkyl, optionally substitutedalkoxy, optionally substituted alkenyl, optionally substituted alkynyl,optionally substituted aryl, optionally substituted aralkyl, —SR¹,—SO₂R¹, —SO₂NR²R³, —SOR¹, —OR¹, —C(O)R¹, —C(O)OR¹, —C(O)NR²R³, —NR²R³ or—NHCOR¹, wherein R¹, R² and R³ are each independently H, optionallysubstituted alkyl, optionally substituted alkenyl, optionallysubstituted alkynyl, optionally substituted aryl or optionallysubstituted aralkyl.

When W, X or Z is optionally substituted phosphoramide it is preferablyunsubstituted or substituted by optionally substituted alkyl, optionallysubstituted aryl or optionally substituted aralkyl. Preferredsubstituents include, for example, methyl, ethyl, n-propyl, iso-propyl,hydroxyethyl, optionally substituted phenyl or optionally substitutedbenzyl.

When W, X or Z is optionally substituted alkoxy it is preferablyoptionally substituted C₁₋₆-alkoxy, optionally substituted by —Cl, —F,—Br, —CN, —OH or —CO₂H. Most preferably Z is unsubstituted C₁₋₆-alkoxy.

When W, X or Z is optionally substituted alkyl it is preferablyoptionally substituted C₁₋₄-alkyl, more preferably C₁₋₄-alkyl optionallysubstituted by halo, hydroxy, carboxy, sulpho or cyano. Examples includemethyl, ethyl, n-propyl, iso-propyl, trifluoromethyl, hydroxyethyl,cyanoethyl, sulphopropyl and carboxyethyl. When Z is optionallysubstituted alkyl it is especially preferably methyl, ethyl ortrifluoromethyl.

When W, X or Z is optionally substituted alkenyl, it is preferablyoptionally substituted C₂-C₄ alkenyl.

When W, X or Z is optionally substituted alkynyl, it is preferablyoptionally substituted C₂-C₆ alkynyl.

When W, X or Z is optionally substituted aryl, it is preferablyoptionally substituted phenyl, optionally substituted naphthyl oroptionally substituted heteroaryl, especially optionally substitutedphenyl or optionally substituted heteroaryl.

Preferred optional substituents on W, X or Z when W, X or Z isoptionally substituted aryl are selected from sulpho, carboxy, nitro,cyano, halo (preferably chloro), alkoxy (preferably C₁₋₆-alkoxy), alkyl(preferably C₁₋₄-alkyl, optionally substituted by halogen (preferablyfluoro)), hydroxy, carboxy, phosphoric acid and sulpho. When W, X or Zis optionally substituted aryl it is especially substituted byC₁₋₄-alkyl, carboxy, phosphoric acid, halogen (preferably fluoro),hydroxy and sulpho.

When W, X or Z is optionally substituted aralkyl, it is preferablyoptionally substituted benzyl.

Preferably W and X are each independently selected from sulpho,sulphonamido, carboxy, carbonamide, halogen, nitro and cyano groups.

Z is most preferably selected from —SH, carboxy, cyano, halo(preferably, bromo, chloro or fluoro), nitro, C₁₋₆alkoxy or C₁₋₄-alkyl,optionally substituted by hydroxy, carboxy, halo (preferably fluoro) orcyano group(s).

R¹, R² and R³ are preferably each independently H, optionallysubstituted C₁₋₄-alkyl or optionally substituted aryl, more preferablyH, C₁₋₄-alkyl optionally substituted by hydroxy, carboxy, sulpho orcyano or phenyl optionally substituted by hydroxy, carboxy, sulpho,nitro, trifluoromethyl or cyano. Examples of groups represented by R¹,R² and R³ include methyl, ethyl, n-propyl, iso-propyl, hydroxyethyl,cyanoethyl, sulphopropyl, carboxyethyl or carboxyphenyl. It isespecially preferred that R¹, R² and R³ are H, optionally substitutedC₁₋₄-alkyl (for example, trifluoromethyl, hydroxyethyl or cyanoethyl),or optionally substituted aryl (for example phenyl optionallysubstituted by carboxy).

It is preferred that the pyridyl ring A is un-substituted or carries oneor more substituents selected from —SH, carboxy, cyano, halo(preferably, bromo, chloro or fluoro), nitro, C₁₋₆-alkoxy or C₁₋₄-alkyl,optionally substituted by hydroxy, carboxy, halo (preferably fluoro) orcyano.

Preferably q is 0, 1, 2, 3 or 4, more preferably q is 0, 1 or 2.

M preferably comprises one or more of the following metals: nickel,chromium, cobalt, copper, zinc, iron or manganese. It is particularlypreferred that M is nickel or copper, most preferably nickel.

Preferably A-N=N—B is chelated to M in the ratio 1:1, 2:1, 2:2 or 2:3respectively, especially in the ratio 1:1 or 2:1 respectively.

When there is more than one ligand of formula A-N=N—B in the metalchelate compound of Formula (1) then the ligands of formula A-N=N—B maybe the same or different but preferably they are the same.

The metal chelate compound of Formula (1) may also comprise 1 or moreadditional ligands. These ligands may be coloured or colourless and whenthere is more than I they may be the same or different.

Preferably n is 0, 1, 2, 3 or 4, more preferably n is 1 or 2. It isespecially preferred that n is 1.

Preferably the compound of Formula (1) is a metal chelate compound ofFormula (4a) or (4b) or a salt thereof:

wherein:

-   M is nickel chelated to the group shown in square brackets;-   X and W are selected from sulpho, sulphonamido, carboxy,    carbonamide, halogen, nitro and cyano groups;-   q is 0, 1 or 2; and-   Z is selected from cyano, C₁₋₄-alkyl, carboxy, nitro, halo and    C₁₋₆-alkoxy groups.

More preferably the compound of Formula (1) is a metal chelate compoundof Formula (5) or a salt thereof:

wherein:

-   M is nickel, chelated to the group shown in square brackets; and-   q is 0, 1 or 2; and-   Z is selected from cyano, C₁₋₄-alkyl, carboxy, nitro, halo and    C₁₋₆-alkoxy groups.

It is especially preferred that the compounds of Formula (1) are magentain colour that is, the compounds posses a λ max in the range 490-570 nm.

The compounds of the invention exhibit particularly good ozone fastness,optical density and light fastness, making them valuable colorants forphotorealistic and other ink jet printing applications.

The compounds of Formula (1) also have good solubility and operabilityin ink jet printers with a low tendency to crust over or block nozzleswhen inks containing the compounds are used in an ink jet printer.

Compounds of Formula (1) are preferably free from fibre reactive groupsbecause no such groups are required. Also fibre reactive groups tend tohydrolyse in ink on long-term storage which can lead to stabilityproblems. The term fibre reactive group is well known in the art and isdescribed for example in EP 0356014 A1. Fibre reactive groups arecapable, under suitable conditions, of reacting with the hydroxyl groupspresent in cellulosic fibres or with the amino groups present in naturalfibres to form a covalent linkage between the fibre and the dye. Asexamples of fibre reactive groups which are preferably absent from thecompounds of Formula (1) there may be mentioned aliphatic sulphonylgroups which contain a sulphate ester group in the beta-position to thesulphur atom, e.g. beta-sulphato-ethylsulphonyl groups, alpha,beta-unsaturated acyl radicals of aliphatic carboxylic acids, forexample acrylic acid, alpha-chloro-acrylic acid, alpha-bromoacrylicacid, propiolic acid, maleic acid and mono- and dichloro maleic; alsothe acyl radicals of acids which contain a substituent which reacts withcellulose in the presence of an alkali, e.g. the radical of ahalogenated aliphatic acid such as chloroacetic acid, beta-chloro andbeta-bromopropionic acids and alpha, beta-dichloro- and dibromopropionicacids or radicals of vinylsulphonyl- or beta-chloroethylsulphonyl- orbeta-sulphatoethyl-sulphonyl-endo-methylene cyclohexane carboxylicacids. Other examples of cellulose reactive groups aretetrafluorocyclobutyl carbonyl, trifluoro-cyclobutenyl carbonyl,tetrafluorocyclobutylethenyl carbonyl, trifluoro-cyclobutenylethenylcarbonyl; activated halogenated 1,3-dicyanobenzene radicals; andheterocyclic radicals which contain 1, 2 or 3 nitrogen atoms in theheterocyclic ring and at least one cellulose reactive substituent on acarbon atom of the ring.

The compounds described herein may exist in tautomeric forms other thanthose shown in this specification. These tautomers are also includedwithin the scope of the present inventions.

The metal chelate compounds of Formula (1) may also exist in differentgeometries e.g. octahedral or square planar. These different geometricforms are also included in the scope of the present invention.

The compounds of Formula (1) may be in the free acid or salt form.Preferred salts are water-soluble, for example alkali metal salts,(especially lithium, sodium, potassium); ammonium, substituted ammoniumand mixed salts thereof. Preferred metal salts are those with sodium,lithium, ammonium and substituted alkyl ammonium salts.

Preferred ammonium and substituted alkyl ammonium salts have cations ofthe formula ⁺NV₄ wherein each V independently is H or optionallysubstituted alkyl, or two groups represented by V are H or optionallysubstituted alkyl and the remaining two groups represented by V,together with the N atom to which they are attached, form a 5- or6-membered ring (preferably a morpholinyl, pyridinyl or piperidinylring).

Preferably each V independently is H or C₁₋₄-alkyl, more preferably H,CH₃ or CH₂CH₃, especially H.

Examples of cations include ⁺NH₄, morpholinium, piperidinium,pyridinium, (CH₃)₃N⁺H, (CH₃)₂N⁺H₂, H₂N⁺(CH₃)(CH₂CH₃), CH₃N⁺H₃,CH₃CH₂N⁺H₃, H₂N⁺(CH₂CH₃)₂, CH₃CH₂CH₂N⁺H₃, (CH₃)₂CHN⁺H₃, N⁺(CH₃)₄,N⁺(CH₂CH₃)₄, N-methyl pyridinium, N,N-dimethyl piperidinium andN,N-dimethyl morpholinium.

It is especially preferred that the compound of Formula (1) is in theform of a sodium, lithium, potassium, ammonium or substituted ammoniumsalt, because we have found that these salts provide prints whichexhibit a high light-fastness when incorporated into an ink jet printingink.

The compounds of Formula (1) may be converted into a salt using knowntechniques. For example, an alkali metal salt of a compound may beconverted into a salt with ammonia or an amine by dissolving an alkalimetal salt of the dye in water and passing the solution through a columnof a suitably modified ion exchange resin.

The compounds of Formula (1) may be prepared using conventionaltechniques for the preparation of metal chelate compounds andnon-stoichiometric mixtures thereof. For example, a suitable methodcomprises mixing together a metal salt and a compound of Formula A-N=N—Bin solution, wherein A and B are as hereinbefore defined.

The product of the above process may be converted to a salt byconventional techniques as hereinbefore described. Alternatively, theproduct may be isolated in its free acid form by acidifying the reactionmixture, preferably using a mineral acid, for example hydrochloric acidand when the product precipitates as a solid it may be separated fromthe mixture by filtration. Unwanted anions may be and preferably areremoved from the product of the above process by dialysis, reverseosmosis, ultra filtration or a combination thereof. Alternatively, theproduct solution is subjected to the above purification directly withoutisolation of the product.

The compounds of Formula A-N=N—B may be prepared by, for example,diazotising the N-oxide of amino-pyridine A-NH₂ to give a diazonium saltand coupling the resultant diazonium salt with a compound of the FormulaH-B, wherein A and B are as hereinbefore defined. The diazotisation ispreferably performed at a temperature below 20° C., more preferably at atemperature in the range −0° C. to 5° C. Preferably the diazotisation isperformed in dilute acid, preferably at a pH below 7. Dilute mineralacid, e.g. HCl or H₂SO₄ or an organic acid for example acetic acid,phosphoric acid or a mixture thereof are often used to achieve thedesired acidic conditions. The N-oxide can then be cleaved to providethe compound of Formula A-N=N—B.

Alternatively, the compounds of Formula (1) can be prepared bydiazotising a compound of formula A-NH₂ to give a diazonium salt e.g.using sodium ethoxide and iso-amyl nitrite, followed by coupling thediazonium salt onto a compound of formula H—B to provide a compound ofFormula A-N=N—B.

Compounds of Formula A-N=N—B can then be converted to the correspondingmetal complexes [A-N=N—B]M by treatment with metal salts, such as forexample nickel (II) chloride or nickel (II) acetate.

The present invention also provides mixtures comprising two or morecompounds of the Formula (1) or salts thereof. Furthermore, thecompounds of Formula (1) may be mixed with commercially available dyes,especially those listed in the Colour Index International, to adjust theshade or other properties as desired.

According to a second aspect of the present invention there is provideda composition comprising:

-   -   (a) one or more compound(s) according to the first aspect of the        present invention; and    -   (b) one or more water-soluble dye(s) other than a compound        according to the first aspect of the invention.

The other water-soluble dye is for example a xanthene dye, an azo or bisazo dye.

Preferred other water-soluble dyes include C.I. Acid Red 50, 52, 87, 91,92, 95, 249 and 289; CI Direct Red 252; pacified Reactive Red 23; C.I.Direct Violet 106 and 107; compounds 100 to 107, 200 and 201 describedon pages 8 and 9 of WO96/24636; compounds 1 to 24 shown described oncolumns 4 to 10 in U.S. Pat. No.5,542,970; compounds 1 to 55 describedon pages 7 to 17 of EP-A-682 088; compounds 1 to 14 shown in Example 1to 6 of EP-A-194,885; compounds 1 to 24 described on pages 8 to 13 ofEP-A-717 089; the compounds described in examples I to 16 in columns. 5to 11 of U.S. Pat. No. 5,262,527; and the dyes described in Examples 1to 21 in WO 94/16021.

The composition according to the second aspect of the present inventionpreferably comprises from 1 to 99, more preferably from 3 to 70 andespecially from 5 to 50 parts in total of Component (a); and from 99 to1, more preferably from 30 to 97 parts and especially 95 to 50 parts intotal of Component (b), wherein the parts are by weight and the sum ofthe parts (a) +(b) =100.

The composition may contain a single dye of Formula (1) or a mixturethereof, as described in the first aspect of the invention. Similarly,the composition may contain a single water-soluble dye or a mixture oftwo or more water-soluble dyes.

The compounds and compositions according to the first and second aspectsof the present invention may be, and preferably are, purified to removeundesirable impurities before they are incorporated into inks for inkjet printing. Conventional techniques may be employed for purification,for example ultrafiltration, reverse osmosis and/or dialysis.

According to a third aspect of the present invention there is providedan ink comprising:

-   -   (i) a compound according to the first aspect of the present        invention, or a composition according to the second aspect of        the invention; and    -   (ii) a liquid medium.

The liquid medium preferably comprises: water; a mixture of water and anorganic solvent; or an organic solvent free from water.

The number of parts by weight of component (i) of the ink is preferablyfrom 0.01 to 30, more preferably 0.1 to 20, especially from 0.5 to 15,and more especially from 1 to 5 parts. The number of parts by weight ofcomponent (ii) is preferably from 99.99 to 70, more preferably from 99.9to 80, especially from 99.5 to 85, and more especially from 99 to 95parts. The number of parts (i)+(ii) is 100 and all parts mentioned hereare by weight.

Preferably component (i) is completely dissolved in component (ii).Preferably component (i) has a solubility in component (ii) at 20° C. ofat least 10%. This allows the preparation of concentrates which may beused to prepare more dilute inks and reduces the chance of thecompound(s) of component (i) of the ink precipitating if evaporation ofthe liquid medium occurs during storage.

When the liquid medium comprises a mixture of water and an organicsolvent, the weight ratio of water to organic solvent is preferably from99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from95:5 to 80:20.

It is preferred that the organic solvent present in the mixture of waterand organic solvent is a water-miscible organic solvent or a mixture ofsuch solvents. Preferred water-miscible organic solvents includeC₁₋₆-alkanols, preferably methanol, ethanol, n-propanol, isopropanol,n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol andcyclohexanol; linear amides, preferably dimethylformamide ordimethylacetamide; ketones and ketone-alcohols, preferably acetone,methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscibleethers, preferably tetrahydrofuran and dioxane; diols, preferably diolshaving from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethyleneglycol, propylene glycol, butylene glycol, pentylene glycol, hexyleneglycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferablydiethylene glycol, triethylene glycol, polyethylene glycol andpolypropylene glycol; triols, preferably glycerol and 1,2,6-hexanetriol;mono-C₁₋₄-alkyl ethers of diols, preferably mono-C₁₋₄-alkyl ethers ofdiols having 2 to 12 carbon atoms, especially 2-methoxyethanol,2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol,2-[2-(2-methoxyethoxy)ethoxy] ethanol, 2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether; cyclic amides,preferably 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone,caprolactam and 1,3-dimethylimidazolidone; cyclic esters, preferablycaprolactone; sulphoxides, preferably dimethyl sulphoxide andsulpholane. Preferably the liquid medium comprises water and 2 or more,especially from 2 to 8, water-miscible organic solvents.

When the liquid medium comprises an organic solvent free from water,(i.e. less than 1% water by weight) the solvent preferably has a boilingpoint of from 30° to 200° C., more preferably of from 40° to 150° C.,especially from 50 to 125° C. The organic solvent may bewater-immiscible, water-miscible or a mixture of such solvents.Preferred water-miscible organic solvents are any of the hereinbeforedescribed water-miscible organic solvents and mixtures thereof.Preferred water-immiscible solvents include, for example, aliphatichydrocarbons; esters, preferably ethyl acetate; chlorinatedhydrocarbons, preferably CH₂Cl₂; and ethers, preferably diethyl ether;and mixtures thereof.

When the liquid medium comprises a water-immiscible organic solvent,preferably a polar solvent is included because this enhances solubilityof the dye in the liquid medium. Examples of polar solvents includeC₁₋₄-alcohols. In view of the foregoing preferences it is especiallypreferred that where the liquid medium is an organic solvent free fromwater it comprises a ketone (especially methyl ethyl ketone) and/or analcohol (especially a C₁₋₄-alkanol, such as ethanol or propanol).

The organic solvent free from water may be a single organic solvent or amixture of two or more organic solvents. It is preferred that when themedium is an organic solvent free from water it is a mixture of 2 to 5different organic solvents. This allows a medium to be selected whichgives good control over the drying characteristics and storage stabilityof the ink.

Inks comprising an organic solvent free from water are particularlyuseful where fast drying times are required and particularly whenprinting onto hydrophobic and non-absorbent substrates, for exampleplastics, metal and glass.

Preferred low melting solid media have a melting point in the range from60° C. to 125° C. Suitable low melting point solids include long chainfatty acids or alcohols, preferably those with C₁₈₋₂₄ chains, andsulphonamides. A compound of Formula (1) may be dissolved in the lowmelting point solid or may be finely dispersed in it.

The inks according to the present invention may of course also containfurther additional components conventionally used in ink jet printinginks, for example viscosity and surface tension modifiers, corrosioninhibitors, biocides, kogation reducing additives, anti-cockle agents toreduce paper curling and surfactants which may be ionic or non-ionic.

The pH of the ink is preferably from 4 to 11, more preferably from 7 to10.

The inks of the present invention preferably form the magenta ink of astandard magenta, yellow, cyan and black ink set. Typically in such anink set the yellow ink will contain C.I. Direct Yellow 86, 142 orPro-Jet™ Fast Yellow 2; the cyan ink will contain C.I. Direct Blue 86,199 or Pro-Jet™ Fast Cyan 2; and the black ink will contain C.I. DirectBlack 199 or Pro-Jet™ Fast Black 2 (Pro-Jet is a trademark of AveciaLimited).

It is preferred that the composition according to the invention is inksuitable for use in an ink-jet printer. Ink suitable for use in anink-jet printer is ink which is able to repeatedly fire through anink-jet printing head without causing blockage of the fine nozzles.

The inks may be incorporated in an ink-jet printer as a highconcentration ink, a low concentration ink or both a high concentrationand a low concentration ink. In the latter case this can lead toimprovements in the resolution and quality of printed images. Thus thepresent invention also provides a composition where component (a) ispresent in an amount of 2.5 to 7 parts, more preferably 2.5 to 5 parts(a high concentration ink) or component (a) is present in an amount of0.5 to 2.4 parts, more preferably 0.5. to 1.5 parts (a low concentrationink).

An ink suitable for use in an ink-jet printer preferably has a viscosityof less than 20 cP, more preferably less than 10 cP, especially lessthan 5 cP, at 25° C.

An ink suitable for use in an ink-jet printer preferably contains lessthan 500 ppm, more preferably less than 250 ppm, especially less than100 ppm, more especially less than 10 ppm in total of divalent andtrivalent metal ions (other than any divalent and trivalent metal ionsbound to a colorant of Formula (1) or any other component of the ink).

Preferably ink suitable for use in an ink-jet printer has been filteredthrough a filter having a mean pore size below 10 μm, more preferablybelow 3 μm, especially below 2 μm, more especially below 1 μm. Thisfiltration removes particulate matter that could otherwise block thefine nozzles found in many ink-jet printers.

Preferably ink suitable for use in an ink-jet printer contains less than500 ppm, more preferably less than 250 ppm, especially less than 100ppm, more especially less than 10 ppm in total of halide ions.

A fourth aspect of the present invention provides a process for printingan image on a substrate comprising applying thereto by means of an inkjet printer an ink containing a compound according to the first aspectof the invention or a composition according to the second aspect of theinvention. The ink used in this process is preferably as defined in thethird aspect of the present invention.

The ink let printer preferably applies the ink to the substrate in theform of droplets which are ejected through a small orifice onto thesubstrate. Preferred ink jet printers are piezoelectric ink jet printersand thermal ink jet printers. In thermal ink jet printers, programmedpulses of heat are applied to the ink in a reservoir by means of aresistor adjacent to the orifice, thereby causing the ink to be ejectedin the form of small droplets directed towards the substrate duringrelative movement between the substrate and the orifice. Inpiezoelectric ink jet printers the oscillation of a small crystal causesejection of the ink from the orifice. Alternately the ink can be ejectedby an electromechanical actuator connected to a moveable paddle orplunger, for example as described in International Patent Application WO00/48938 and International Patent Application WO 00/55089.

The substrate is preferably paper, plastic, a textile, metal or glass,more preferably paper, an overhead projector slide or a textilematerial, especially paper. Preferred papers are plain or treated paperswhich may have an acid, alkaline or neutral character. Glossy papers areespecially preferred. More especially photographic quality paper ispreferred

Examples of commercially available papers include, HP Premium CoatedPaper, HP Photopaper (all available from Hewlett Packard Inc.), StylusPro 720 dpi Coated Paper, Epson Photo Quality Glossy Film, Epson PhotoQuality Glossy Paper (available from Seiko Epson Corp.), Canon HR 101High Resolution Paper, Canon GP 201 Glossy Paper, Canon HG 101 HighGloss Film (all available from Canon Inc.), Wiggins Conqueror paper(available from Wiggins Teape Ltd), Xerox Acid Paper and Xerox Alkalinepaper (available from Xerox).

A fifth aspect of the present invention provides a substrate, preferablya paper, an overhead projector slide or a textile material, printed withan ink according to the third aspect of the present invention or bymeans of the process according to the fourth aspect of the presentinvention.

It is especially preferred that the fifth aspect of the invention is aphotographic quality print.

According to a sixth aspect of the present invention there is providedan ink jet printer cartridge comprising a chamber and ink, wherein theink is present in the chamber and the ink contains a compound or acomposition according to the first or second aspect of the presentinvention. Preferably the ink is as defined in the third aspect of thepresent invention.

According to a seventh aspect of the present invention there is providedan ink jet printer containing an ink jet printer cartridge, wherein theink jet printer cartridge is as defined in the sixth aspect of thepresent invention.

The invention is further illustrated by the following Examples in whichall parts and percentages are by weight unless otherwise stated.

EXAMPLE 1 Preparation of Compound (1) wherein M is Nickel

Compound 1 was prepared according to the stages (a) and (b):

Stage (a): Preparation of2-hydroxy-1-[pyridin-2-yldiazenyl]naphthalene-3.6-disulfonic acid

2-Hydroxy-l-[pyridin-2-yldiazenyl]naphthalene (20 g, 0.08 mol) was addedover 30 minutes to ice cold fuming sulphuric acid (20% sulphur trioxide,150 ml). Once the addition was complete the reaction temperature wasslowly raised to 60° C. and held at that temperature for 1.5 hours. Themixture was allowed to cool before being added to ice (1 kg) to give anorange suspension. The solid was collected by filtration, washed withsodium chloride solution and acetone to give 57 g of an orange solid(91% yield, 52% strength).

Stage (b): Preparation of Compound (1)

The product from stage (a) (5 g, 6.4 mmol) was dissolved in water at pH6 (150 ml). An aqueous solution of nickel chloride hexahydrate (8.5 mlof a 0.4 mol dm⁻³ solution) was added dropwise causing the colour tobecome deeper and the pH to fall. The pH was restored to pH 6-7 and thereaction mixture stirred at 70-80° C. for 2 hours. After cooling the dyewas precipitated by the addition of sodium chloride and collected byfiltration. The dye was reconstituted and dialysed to low conductivitythrough a dialysis membrane, to give 1 g of solid. λ_(max)(water) 523,562 nm.

EXAMPLE 2 Preparation of Compound (2) wherein M is Nickel

Example 2 was prepared by following the same procedure as described forcompound (1) of example 1, with the exception that in stage (b) 17.5 mlof a 0.4 mol dm⁻³ nickel chloride solution was used. 2.1 g of solid wascollected, λ_(max)(water) 518, 555 nm.

Comparative Dye 1

Comparative Dye 1 was prepared as described in Example 4 of EP1270676Aand is of Formula:

Comparative Dye 2

Comparative Dye 2 was prepared as described for Example IV of EP0902064Band is of Formula:

EXAMPLE 3 Inks and Inkjet Printing

The dyes described in Examples 1 and 2 and Comparative Dyes 1 and 2 wereeach converted into the corresponding inks were by dissolving 3.5 partsof each in 96.5 parts of a liquid medium comprising:

-   5 parts 2-pyrrolidone;-   5 parts thiodiglycol;-   2 parts Surfynol™ 465 (a non-ionic surfactant available from Air    Products Inc.);-   88 parts water: and-   adjusted to pH 9.5 with ammonium hydroxide.

The inks so prepared were designated as Ink 1, Ink 2, Comparative Ink 1and Comparative Ink 2 depending on which dye was incorporated therein

Ink-Jet Printing

Inks 1 and 2 and the Comparative Inks I and 2 were filtered through a0.45 micron nylon filters and then incorporated into empty ink-jet printcartridges using a syringe.

The inks were then printed using an HP560C printer onto CanonProfessional Photo Paper PR101 at 70% strength.

These prints were tested for ozone fastness by exposure to 1 ppm ozoneat 40° C., 50% relative humidity for 24 hrs in a Hampden 903 Ozonecabinet. The prints were also tested for light fastness by exposure to aXenon Arc lamp for 100 hours in an Atlas Ci5000 Weatherometer. Fastnessof the printed ink to ozone and light was judged by the difference inthe colour co-ordinates before and after exposure.

Colour measurements of the prints before and after exposure to ozone andlight were performed using a Gretag spectrolino spectrophotometer set tothe following parameters: Measuring Geometry 0°/45° Spectral Range400-700 nm Spectral Interval 20 nm Illuminant D65 Observer 2° (UE 1931)Density ANSI A External Filler None

Ozone and light fastness were assessed by the change in the shade of theprint (ΔE) as judged via the colour co-ordinates of the print, where alower figure indicates higher fastness. This change ΔE is calculatedusing the relationship ΔE=((Δa*)²+(Δb*)²+(ΔL*)²)^(0.5). Results for theozone and light fastness of the prints are shown below. TABLE 1 ΔE Ozonefastness ΔE Light fastness Ink 1 1 13 Ink 2 6 26 Comparative Ink 1 15 27Comparative Ink 2 16 36

Table 1 shows that the inks of the present invention have an improvedozone and light fastness when compared to similar analogues.

Other Inks

The inks described in Tables A and B may be prepared wherein theCompound described in the first column is the Compound made in the aboveExamples of the same number. Numbers quoted in the second column onwardsrefer to the number of parts of the relevant ingredient and all partsare by weight. The inks may be applied to paper by thermal or piezo inkjet printing.

The following abbreviations are used in Table A and B:

PG=propylene glycol

DEG=diethylene glycol

NMP=N-methyl pyrollidone

DMK=dimethylketone

IPA=isopropanol

MEOH=methanol

2P=2-pyrollidone

MIBK=methylisobutyl ketone

P12 =propane-1,2-diol

BDL=butane-2,3-diol

CET=cetyl ammonium bromide

PHO=Na₂HPO₄ and

TBT=tertiary butanol

TDG=thiodiglycol TABLE A Dye Na Dye Content Water PG DEG NMP DMK NaOHStearate IPA MEOH 2P MIBK 1 2.0 80 5 6 4 5 2 3.0 90 5 5 0.2 2 10.0 85 33 3 5 1 1 2.1 91 8 1 1 3.1 86 5 0.2 4 5 1 1.1 81 9 0.5 0.5 9 2 2.5 60 415 3 3 6 10 5 4 1 5 65 20 10 1 2.4 75 5 4 5 6 5 2 4.1 80 3 5 2 10 0.3 23.2 65 5 4 6 5 4 6 5 1 5.1 96 4 2 10.8 90 5 5 1 10.0 80 2 6 2 5 1 4 21.8 80 5 15 2 2.6 84 11 5 1 3.3 80 2 10 2 6 1 12.0 90 7 0.3 3 2 5.4 69 220 2 1 3 3 2 6.0 91 4 5

TABLE B Dye Dye Content Water PG DEG NMP CET TBT TDG BDL PHO 2P PI2 13.0 80 15 0.2 5 2 9.0 90 5 1.2 5 2 1.5 85 5 5 0.15 5.0 0.2 2 2.5 90 6 40.12 1 3.1 82 4 8 0.3 6 1 0.9 85 10 5 0.2 2 8.0 90 5 5 0.3 2 4.0 70 10 41 4 11 1 2.2 75 4 10 3 2 6 2 10.0 91 6 3 1 9.0 76 9 7 3.0 0.95 5 1 5.078 5 11 6 2 5.4 86 7 7 2 2.1 70 5 5 5 0.1 0.2 0.1 5 0.1 5 1 2.0 90 10 12 88 10 2 5 78 5 12 5 1 8 70 2 8 15 5 1 10 80 8 12 1 10 80 10

1. A metal chelate compound of Formula (1) or a salt thereof:[A-N=N—B] M   Formula (1) wherein: A is an optionally substitutedpyridyl ring; and B is of the Formula (2):

wherein: X and W are substituents other than H; M is a metal chelated toA-N=N—B; and n is 0 to
 4. 2. A compound according to claim 1 wherein Ais of the Formula (3):

wherein: q is 0, 1, 2, 3 or 4; and each Z independently is a substituentother than H.
 3. A compound according to either claim 1 wherein W, X andZ are each independently selected from CF₃, —OH, —Br, —Cl, —F, —CN,—NO₂, phosphoric acid, sulpho, optionally substituted phosphoramide,optionally substituted alkyl, optionally substituted alkoxy, optionallysubstituted alkenyl, optionally substituted alkynyl, optionallysubstituted aryl, optionally substituted aralkyl, —SR¹, —SO₂R¹,—SO₂NR²R³, —SOR¹, —OR¹, —C(O)R¹, —C(O)OR¹, —C(O)NR²R³ —NR²R³ or —NHCOR¹,wherein R¹, R² and R³ are each independently H, optionally substitutedalkyl, optionally substituted alkenyl, optionally substituted alkynyl,optionally substituted aryl or optionally substituted aralkyl.
 4. Acompound according to claim 1 wherein Z is selected from —SH, carboxy,cyano, halo, nitro, C₁₋₆-alkoxy or C₁₋₄-alkyl, optionally substituted byhydroxy, carboxy, halo or cyano group(s).
 5. A compound according toclaim 1 wherein W and X are each independently selected from sulpho,sulphonamido, carboxy, carbonamide, halogen, nitro and cyano groups. 6.A compound according to claim 1 wherein in the metal chelate compound ofFormula (1) A-N=N—B is chelated to M in the ratio 1:1 or 2:1respectively.
 7. A compound according to claim 1 wherein M is nickel,chromium, cobalt, copper, zinc, iron or manganese.
 8. A compoundaccording to claim 1 wherein M is nickel.
 9. A metal chelate compoundaccording to claim 1 of Formula (4a) or (4b) or a salt thereof:

wherein: M is nickel, chelated to the group shown in square brackets;and X and W are selected from sulpho, sulphonamido, carboxy,carbonamide, halogen, nitro and cyano groups; q is 0, 1 or 2; and Z isselected from cyano, C₁₋₄-alkyl, carboxy, nitro, halo and C₁₋₆-alkoxygroups.
 10. A compound according to claim 1 of Formula (5) or a saltthereof:

wherein: M is nickel, chelated to the group shown in square brackets;and q is 0, 1 or 2; and Z is selected from cyano, C₁₋₄-alkyl, carboxy,nitro, halo and C₁₋₆-alkoxy groups.
 11. A composition comprising: (a)one or more compound(s) according to claim 1; and (b) one or morewater-soluble dye(s) other than a compound according to (a).
 12. An inkcomprising: (a) a compound according to claim 1, or a compositionaccording to claim 11; and (b) a liquid medium.
 13. A process forprinting an image on a substrate comprising applying thereto by means ofan ink jet printer an ink according to claim
 12. 14. A substrate printedwith an ink according to claim
 11. 15. An ink jet printer cartridgecomprising a chamber and ink, wherein the ink is present in the chamberand the ink is as defined in claim
 12. 16. An ink jet printer containingan ink jet printer cartridge, wherein the ink jet printer cartridge isas defined in claim
 15. 17. A substrate printed by means of the processaccording to claim 13.